This invention relates generally to radiation detectors. More particularly, the application relates to a dual range neutron detection device.
It is necessary for detection of transitions from low neutron fields to high neutron fields to use two separate detectors, namely a 3He detector and a boron-lined detector. For low level neutron fluxes, the high efficiency from 3He gives an optimal performance. However, for high levels of neutron fluxes, the 3He reaction is too sensitive, making the 3He detector unusable. In such instances, a less efficient 10B proportional counter may be employed. In practice, this means that either two detectors must be employed in the system or one type of detector must be removed and replaced by the other type of detector. This is inconvenient and time-consuming, and sometimes is not possible if space is limited.
In some situations, assay of nuclear materials requires measurements of low levels of neutrons in a high gamma environment. The 3He neutron proportional counter is a high sensitivity detector which may be used for low level neutron measurements. However, this detector has a high enough sensitivity to gamma radiation in these applications to make it virtually unusable. The primary cause of gamma response in detectors is the interaction of gamma rays with the construction materials of the detectors. The unique construction of this detector reduces the response to gamma radiation, allowing it to b used in high gamma environments.
A need exists therefore for a single detector which incorporates the features of both designs and is capable of performing both functions. This would avoid the need to install each of the different types of detectors for the particular application, or remove one detector from a system and replace it with the other. A single detector would be advantageous where space limitations prevent the use of two detectors or changing detectors is difficult and/or impractical. The present invention seeks to satisfy that need.
According to one aspect, there is provided a dual range neutron detector, comprising a chamber which serves as a cathode, an insulator at either end of the chamber, an anode located within the chamber and supported by the insulators, and an electrical connector mounted on one of the insulators for transmission of a signal collected by the anode. The chamber is filled with 3He and an inner wall of the chamber is provided with a boron coating.
According to another aspect, there is provided a method of measuring neutron levels in nuclear fuel, which includes providing a dual range neutron detector as defined above proximate the nuclear fuel to be measured, and detecting the neutron level in the fuel. Typically, fuel is spent nuclear fuel.